xref: /openbmc/linux/arch/sparc/kernel/unaligned_32.c (revision b34e08d5)
1 /*
2  * unaligned.c: Unaligned load/store trap handling with special
3  *              cases for the kernel to do them more quickly.
4  *
5  * Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu)
6  * Copyright (C) 1996 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
7  */
8 
9 
10 #include <linux/kernel.h>
11 #include <linux/sched.h>
12 #include <linux/mm.h>
13 #include <asm/ptrace.h>
14 #include <asm/processor.h>
15 #include <asm/uaccess.h>
16 #include <linux/smp.h>
17 #include <linux/perf_event.h>
18 
19 enum direction {
20 	load,    /* ld, ldd, ldh, ldsh */
21 	store,   /* st, std, sth, stsh */
22 	both,    /* Swap, ldstub, etc. */
23 	fpload,
24 	fpstore,
25 	invalid,
26 };
27 
28 static inline enum direction decode_direction(unsigned int insn)
29 {
30 	unsigned long tmp = (insn >> 21) & 1;
31 
32 	if(!tmp)
33 		return load;
34 	else {
35 		if(((insn>>19)&0x3f) == 15)
36 			return both;
37 		else
38 			return store;
39 	}
40 }
41 
42 /* 8 = double-word, 4 = word, 2 = half-word */
43 static inline int decode_access_size(unsigned int insn)
44 {
45 	insn = (insn >> 19) & 3;
46 
47 	if(!insn)
48 		return 4;
49 	else if(insn == 3)
50 		return 8;
51 	else if(insn == 2)
52 		return 2;
53 	else {
54 		printk("Impossible unaligned trap. insn=%08x\n", insn);
55 		die_if_kernel("Byte sized unaligned access?!?!", current->thread.kregs);
56 		return 4; /* just to keep gcc happy. */
57 	}
58 }
59 
60 /* 0x400000 = signed, 0 = unsigned */
61 static inline int decode_signedness(unsigned int insn)
62 {
63 	return (insn & 0x400000);
64 }
65 
66 static inline void maybe_flush_windows(unsigned int rs1, unsigned int rs2,
67 				       unsigned int rd)
68 {
69 	if(rs2 >= 16 || rs1 >= 16 || rd >= 16) {
70 		/* Wheee... */
71 		__asm__ __volatile__("save %sp, -0x40, %sp\n\t"
72 				     "save %sp, -0x40, %sp\n\t"
73 				     "save %sp, -0x40, %sp\n\t"
74 				     "save %sp, -0x40, %sp\n\t"
75 				     "save %sp, -0x40, %sp\n\t"
76 				     "save %sp, -0x40, %sp\n\t"
77 				     "save %sp, -0x40, %sp\n\t"
78 				     "restore; restore; restore; restore;\n\t"
79 				     "restore; restore; restore;\n\t");
80 	}
81 }
82 
83 static inline int sign_extend_imm13(int imm)
84 {
85 	return imm << 19 >> 19;
86 }
87 
88 static inline unsigned long fetch_reg(unsigned int reg, struct pt_regs *regs)
89 {
90 	struct reg_window32 *win;
91 
92 	if(reg < 16)
93 		return (!reg ? 0 : regs->u_regs[reg]);
94 
95 	/* Ho hum, the slightly complicated case. */
96 	win = (struct reg_window32 *) regs->u_regs[UREG_FP];
97 	return win->locals[reg - 16]; /* yes, I know what this does... */
98 }
99 
100 static inline unsigned long safe_fetch_reg(unsigned int reg, struct pt_regs *regs)
101 {
102 	struct reg_window32 __user *win;
103 	unsigned long ret;
104 
105 	if (reg < 16)
106 		return (!reg ? 0 : regs->u_regs[reg]);
107 
108 	/* Ho hum, the slightly complicated case. */
109 	win = (struct reg_window32 __user *) regs->u_regs[UREG_FP];
110 
111 	if ((unsigned long)win & 3)
112 		return -1;
113 
114 	if (get_user(ret, &win->locals[reg - 16]))
115 		return -1;
116 
117 	return ret;
118 }
119 
120 static inline unsigned long *fetch_reg_addr(unsigned int reg, struct pt_regs *regs)
121 {
122 	struct reg_window32 *win;
123 
124 	if(reg < 16)
125 		return &regs->u_regs[reg];
126 	win = (struct reg_window32 *) regs->u_regs[UREG_FP];
127 	return &win->locals[reg - 16];
128 }
129 
130 static unsigned long compute_effective_address(struct pt_regs *regs,
131 					       unsigned int insn)
132 {
133 	unsigned int rs1 = (insn >> 14) & 0x1f;
134 	unsigned int rs2 = insn & 0x1f;
135 	unsigned int rd = (insn >> 25) & 0x1f;
136 
137 	if(insn & 0x2000) {
138 		maybe_flush_windows(rs1, 0, rd);
139 		return (fetch_reg(rs1, regs) + sign_extend_imm13(insn));
140 	} else {
141 		maybe_flush_windows(rs1, rs2, rd);
142 		return (fetch_reg(rs1, regs) + fetch_reg(rs2, regs));
143 	}
144 }
145 
146 unsigned long safe_compute_effective_address(struct pt_regs *regs,
147 					     unsigned int insn)
148 {
149 	unsigned int rs1 = (insn >> 14) & 0x1f;
150 	unsigned int rs2 = insn & 0x1f;
151 	unsigned int rd = (insn >> 25) & 0x1f;
152 
153 	if(insn & 0x2000) {
154 		maybe_flush_windows(rs1, 0, rd);
155 		return (safe_fetch_reg(rs1, regs) + sign_extend_imm13(insn));
156 	} else {
157 		maybe_flush_windows(rs1, rs2, rd);
158 		return (safe_fetch_reg(rs1, regs) + safe_fetch_reg(rs2, regs));
159 	}
160 }
161 
162 /* This is just to make gcc think panic does return... */
163 static void unaligned_panic(char *str)
164 {
165 	panic(str);
166 }
167 
168 /* una_asm.S */
169 extern int do_int_load(unsigned long *dest_reg, int size,
170 		       unsigned long *saddr, int is_signed);
171 extern int __do_int_store(unsigned long *dst_addr, int size,
172 			  unsigned long *src_val);
173 
174 static int do_int_store(int reg_num, int size, unsigned long *dst_addr,
175 			struct pt_regs *regs)
176 {
177 	unsigned long zero[2] = { 0, 0 };
178 	unsigned long *src_val;
179 
180 	if (reg_num)
181 		src_val = fetch_reg_addr(reg_num, regs);
182 	else {
183 		src_val = &zero[0];
184 		if (size == 8)
185 			zero[1] = fetch_reg(1, regs);
186 	}
187 	return __do_int_store(dst_addr, size, src_val);
188 }
189 
190 extern void smp_capture(void);
191 extern void smp_release(void);
192 
193 static inline void advance(struct pt_regs *regs)
194 {
195 	regs->pc   = regs->npc;
196 	regs->npc += 4;
197 }
198 
199 static inline int floating_point_load_or_store_p(unsigned int insn)
200 {
201 	return (insn >> 24) & 1;
202 }
203 
204 static inline int ok_for_kernel(unsigned int insn)
205 {
206 	return !floating_point_load_or_store_p(insn);
207 }
208 
209 static void kernel_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
210 {
211 	unsigned long g2 = regs->u_regs [UREG_G2];
212 	unsigned long fixup = search_extables_range(regs->pc, &g2);
213 
214 	if (!fixup) {
215 		unsigned long address = compute_effective_address(regs, insn);
216         	if(address < PAGE_SIZE) {
217                 	printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference in mna handler");
218         	} else
219                 	printk(KERN_ALERT "Unable to handle kernel paging request in mna handler");
220 	        printk(KERN_ALERT " at virtual address %08lx\n",address);
221 		printk(KERN_ALERT "current->{mm,active_mm}->context = %08lx\n",
222 			(current->mm ? current->mm->context :
223 			current->active_mm->context));
224 		printk(KERN_ALERT "current->{mm,active_mm}->pgd = %08lx\n",
225 			(current->mm ? (unsigned long) current->mm->pgd :
226 			(unsigned long) current->active_mm->pgd));
227 	        die_if_kernel("Oops", regs);
228 		/* Not reached */
229 	}
230 	regs->pc = fixup;
231 	regs->npc = regs->pc + 4;
232 	regs->u_regs [UREG_G2] = g2;
233 }
234 
235 asmlinkage void kernel_unaligned_trap(struct pt_regs *regs, unsigned int insn)
236 {
237 	enum direction dir = decode_direction(insn);
238 	int size = decode_access_size(insn);
239 
240 	if(!ok_for_kernel(insn) || dir == both) {
241 		printk("Unsupported unaligned load/store trap for kernel at <%08lx>.\n",
242 		       regs->pc);
243 		unaligned_panic("Wheee. Kernel does fpu/atomic unaligned load/store.");
244 	} else {
245 		unsigned long addr = compute_effective_address(regs, insn);
246 		int err;
247 
248 		perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);
249 		switch (dir) {
250 		case load:
251 			err = do_int_load(fetch_reg_addr(((insn>>25)&0x1f),
252 							 regs),
253 					  size, (unsigned long *) addr,
254 					  decode_signedness(insn));
255 			break;
256 
257 		case store:
258 			err = do_int_store(((insn>>25)&0x1f), size,
259 					   (unsigned long *) addr, regs);
260 			break;
261 		default:
262 			panic("Impossible kernel unaligned trap.");
263 			/* Not reached... */
264 		}
265 		if (err)
266 			kernel_mna_trap_fault(regs, insn);
267 		else
268 			advance(regs);
269 	}
270 }
271 
272 static inline int ok_for_user(struct pt_regs *regs, unsigned int insn,
273 			      enum direction dir)
274 {
275 	unsigned int reg;
276 	int check = (dir == load) ? VERIFY_READ : VERIFY_WRITE;
277 	int size = ((insn >> 19) & 3) == 3 ? 8 : 4;
278 
279 	if ((regs->pc | regs->npc) & 3)
280 		return 0;
281 
282 	/* Must access_ok() in all the necessary places. */
283 #define WINREG_ADDR(regnum) \
284 	((void __user *)(((unsigned long *)regs->u_regs[UREG_FP])+(regnum)))
285 
286 	reg = (insn >> 25) & 0x1f;
287 	if (reg >= 16) {
288 		if (!access_ok(check, WINREG_ADDR(reg - 16), size))
289 			return -EFAULT;
290 	}
291 	reg = (insn >> 14) & 0x1f;
292 	if (reg >= 16) {
293 		if (!access_ok(check, WINREG_ADDR(reg - 16), size))
294 			return -EFAULT;
295 	}
296 	if (!(insn & 0x2000)) {
297 		reg = (insn & 0x1f);
298 		if (reg >= 16) {
299 			if (!access_ok(check, WINREG_ADDR(reg - 16), size))
300 				return -EFAULT;
301 		}
302 	}
303 #undef WINREG_ADDR
304 	return 0;
305 }
306 
307 static void user_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
308 {
309 	siginfo_t info;
310 
311 	info.si_signo = SIGBUS;
312 	info.si_errno = 0;
313 	info.si_code = BUS_ADRALN;
314 	info.si_addr = (void __user *)safe_compute_effective_address(regs, insn);
315 	info.si_trapno = 0;
316 	send_sig_info(SIGBUS, &info, current);
317 }
318 
319 asmlinkage void user_unaligned_trap(struct pt_regs *regs, unsigned int insn)
320 {
321 	enum direction dir;
322 
323 	if(!(current->thread.flags & SPARC_FLAG_UNALIGNED) ||
324 	   (((insn >> 30) & 3) != 3))
325 		goto kill_user;
326 	dir = decode_direction(insn);
327 	if(!ok_for_user(regs, insn, dir)) {
328 		goto kill_user;
329 	} else {
330 		int err, size = decode_access_size(insn);
331 		unsigned long addr;
332 
333 		if(floating_point_load_or_store_p(insn)) {
334 			printk("User FPU load/store unaligned unsupported.\n");
335 			goto kill_user;
336 		}
337 
338 		addr = compute_effective_address(regs, insn);
339 		perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);
340 		switch(dir) {
341 		case load:
342 			err = do_int_load(fetch_reg_addr(((insn>>25)&0x1f),
343 							 regs),
344 					  size, (unsigned long *) addr,
345 					  decode_signedness(insn));
346 			break;
347 
348 		case store:
349 			err = do_int_store(((insn>>25)&0x1f), size,
350 					   (unsigned long *) addr, regs);
351 			break;
352 
353 		case both:
354 			/*
355 			 * This was supported in 2.4. However, we question
356 			 * the value of SWAP instruction across word boundaries.
357 			 */
358 			printk("Unaligned SWAP unsupported.\n");
359 			err = -EFAULT;
360 			break;
361 
362 		default:
363 			unaligned_panic("Impossible user unaligned trap.");
364 			goto out;
365 		}
366 		if (err)
367 			goto kill_user;
368 		else
369 			advance(regs);
370 		goto out;
371 	}
372 
373 kill_user:
374 	user_mna_trap_fault(regs, insn);
375 out:
376 	;
377 }
378